10-1 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Chapter 10 Lecture Outline
See PowerPoint Image Slides for all figures and tables pre-inserted
into PowerPoint without notes. Slide 2 10-2 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Meiosis, Genes, and Alleles Genetics is the study of
inheritance. Genetics can predict how genes may be passed on to
future generations. Requires an understanding of How genes are
organized on chromosomes How chromosomes are passed on during
meiosis Slide 3 10-3 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Different Ways to
Study Genes A gene is A piece of DNA that has the necessary
information to code for a protein and regulate its expression Found
on a chromosome Related to a characteristic of an organism These
characteristics result from the work of a particular protein. Eye
color Flower color Pea shape Slide 4 10-4 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
What Is an allele? One particular gene may exist in multiple forms.
An allele is A specific version of a gene Example: Earlobe-shaped
gene There are two different alleles for this gene. Attached
earlobe Free earlobe Different alleles code for different forms of
the same protein. The different forms of the protein function
differently. Result in different characteristics Slide 5 10-5
Copyright The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. What Is an allele? Slide 6 10-6 Copyright
The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Genomes and Meiosis The sum total of an
organisms genes is called its genome. In sexually reproducing
organisms, the genome is diploid. This means that they have two
copies of every gene. The copies may not be identical, so one
individual could have two different alleles. Single-celled
organisms and sex-cells are haploid. They only have one copy of
each gene. They only have one allele. Slide 7 10-7 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Genomes and Meiosis Sex cells are sperm and egg. Sperm and
egg only receive one set of that individuals genes. When haploid
egg joins with haploid sperm (fertilization), a diploid zygote
results. The zygote receives half of its genome from the sperm and
half of its genome from the egg. Has a unique set of genes,
different from the parents Slide 8 10-8 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Genomes and Meiosis Meiosis is the process by which egg and sperm
are made. Homologous chromosomes can carry different alleles. When
the homologous chromosomes separate during meiosis, the alleles are
delivered to different sex cells. Slide 9 10-9 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Homologous Chromosomes Slide 10 10-10 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Fundamentals of Genetics Three questions allow us to
predict how a trait will be inherited: What alleles do the parents
have for that trait? What alleles will be present in the gametes
that the parents produce? What is the likelihood that gametes with
specific combinations of alleles will be fertilized? Slide 11 10-11
Copyright The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Phenotype vs. Genotype Diploid organisms
have two copies of every gene. This means that one individual can
have two different versions of a gene. The term allele is used to
identify different versions of a gene. Genotype describes the
combination of alleles present in the organisms cells. Phenotype
describes the organisms appearance. This is a result of its
genotype. Slide 12 10-12 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Example: Earlobe
Shape Phenotypes: free or attached Genotypes: EE (two alleles for
free earlobes) Earlobes will be free ee (two alleles for attached
earlobes) Earlobes will be attached Ee (one allele for free and one
allele for attached) Earlobes will be free The free earlobe allele
is dominant. It out-performs the attached earlobe allele. The
attached earlobe allele is recessive. Masked by the dominant allele
when present together Only expressed when two copies are present
Slide 13 10-13 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Homozygous vs. Heterozygous
Homozygous Two copies of the same allele EE is homozygous dominant.
ee is homozygous recessive. Heterozygous Two different alleles Ee
Slide 14 10-14 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Predicting Genotype from
Phenotype An individual with the dominant phenotype Could be
homozygous dominant Could be heterozygous A person with free
earlobes could be EE or Ee An individual with the recessive
phenotype Is always homozygous recessive A person with attached
earlobes is ee. Slide 15 10-15 Copyright The McGraw-Hill Companies,
Inc. Permission required for reproduction or display. Predicting
Gametes from Meiosis The Law of Segregation: Alleles will separate
during meiosis. Each gamete will receive one allele. An EE
individual will make gametes that have E. An ee individual will
make gametes that have e. An Ee individual will make gametes that
have either E or e. Slide 16 10-16 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Predicting Offspring from Fertilization Fertilization is the
process of two haploid sex cells joining to form a diploid zygote.
The genotype of the offspring will be determined by the alleles
carried by the gametes. A genetic cross is a planned mating between
two organisms. The outcome of a given cross is predicted by a
Punnett Square. Single-factor crosses track the inheritance of one
trait. Also called monohybrid crosses Double-factor crosses track
the inheritance of two traits. Also called dihybrid crosses Slide
17 10-17 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Punnett Square Slide 18 10-18
Copyright The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Probability vs. Possibility Probability is
the mathematical chance that an event will happen. Expressed as a
percent, or a fraction Probability = the # of events that can
produce a given outcome/the total # of possible outcomes. The
probability of two or more events occurring simultaneously is the
product of their individual probabilities. Possibility states that
an event can happen; probability states how likely the event is to
happen. Slide 19 10-19 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. The First
Geneticist: Gregor Mendel Mendel was a monk who was the first to
describe the basic patterns of inheritance. Studied inheritance in
garden pea plants Studied several different phenotypes Identified
the concepts of dominance and recessiveness Didnt know about genes
or chromosomes Identified patterns by mathematical analysis of the
data Slide 20 10-20 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Mendels Experiment
Parental (P) generation A pure-breeding purple-flowered plant mated
with a pure- breeding white-flowered plant. CC x cc First filial
generation (F1) All offspring had purple flowers (Cc). They were
allowed to self-pollinate. Cc x Cc Second filial generation (F2) of
the offspring were purple of the offspring were white 3:1 ratio,
purple: white Mendel saw this pattern with any of the traits he
studied. Slide 21 10-21 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Dominant and
Recessive Traits in Pea Plants Slide 22 10-22 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Mendels Conclusions Organisms have two pieces of genetic
information for each trait. We know these as alleles. The Law of
Dominance Some alleles mask other alleles. Gametes fertilize
randomly. The Law of Segregation Alleles separate into gametes
during meiosis. Slide 23 10-23 Copyright The McGraw-Hill Companies,
Inc. Permission required for reproduction or display. Solving
Genetics Problems: Single-Factor Crosses The pod color of some pea
plants is inherited so that green pods are dominant to yellow pods.
A pea plant that is heterozygous for green pods is crossed to a pea
plant that produces yellow pods. What proportion of the offspring
will have green pods? Slide 24 10-24 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Step I: Make a Gene Key Slide 25 10-25 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Step 2: Identify Information in the Problem A green plant is
crossed with a yellow plant. The green pod plant is heterozygous.
Gg The yellow pod plant is homozygous. gg The cross is Gg x gg.
Slide 26 10-26 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Step 3: Determine Possible
Gametes from Each Parent Heterozygous green pod parent (Gg) Could
make gametes with G or g Homozygous yellow pod parent (gg) Could
make gametes with g Slide 27 10-27 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Step 4: Create a Punnett Square Put the gametes from one parent on
one side. Put the gametes from the other parent on the other side.
Simulate random fertilization by crossing the possible gametes.
This will determine offspring phenotypes. Slide 28 10-28 Copyright
The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Step 5: Determine Offspring Phenotypes and
Calculate Probability Use the gene key to determine the phenotype
of the offspring you predicted. Revisit the question to calculate
the answer to the question. What proportion of offspring will
produce green pods? The answer is 50%. Slide 29 10-29 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Cross #2: PKU The normal condition is to convert
phenylalanine to tyrosine. It is dominant over the condition for
PKU. If both parents are heterozygous for PKU, what is the
probability that they will have A child that is normal? A child
with PKU? Slide 30 10-30 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Solution Pathway
Slide 31 10-31 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Double-Factor Crosses
Dihybrid crosses track the inheritance of two traits. Mendel used
dihybrid crosses to identify the law of independent assortment.
States that alleles of one character separate independently of
alleles of another character Only true when the genes for the two
characters are on different chromosomes Slide 32 10-32 Copyright
The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Solving Double-Factor Crosses When solving
a double-factor cross, you must obey the law of segregation and the
law of independent assortment. Each gamete must receive only one
copy of each gene. All combinations of alleles for A and B must be
considered. Consider an individual whose genotype is AaBb. Gametes
could receive AB, Ab, aB, or ab. Slide 33 10-33 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. A Sample Double-Factor Cross In humans the allele for free
earlobes is dominant over the allele for attached earlobes. The
allele for dark hair dominates the allele for light hair. If both
parents are heterozygous for earlobe shape and hair color, what
types of offspring can they produce, and what is the probability
for each type? Slide 34 10-34 Copyright The McGraw-Hill Companies,
Inc. Permission required for reproduction or display. Solving the
Double-Factor Cross Start by creating a gene key for each gene.
Slide 35 10-35 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Solving the Double-Factor
Cross Slide 36 10-36 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Solving the
Double-Factor Cross Slide 37 10-37 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Modified Mendelian Patterns Some alleles have consistent
dominant/recessive patterns like Mendel observed. However, many
traits are not inherited following these patterns. Several other
types of inheritance patterns exist. Slide 38 10-38 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Codominance Some alleles are codominant. Both phenotypes
are expressed together in a heterozygote. This will result in three
phenotypes. Horse color D R D R is chestnut color D R D W is white
color D W D W is palomino-colored (chestnut with white mane and
tail) Slide 39 10-39 Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display. Codominance Slide
40 10-40 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Incomplete Dominance Occurs
when the phenotype of the heterozygote is intermediate between the
two homozygotes Appears as if the heterozygotes are blends of the
homozygotes Snapdragons F w F w =white flower F r F r =red flower F
w F r =pink flower Slide 41 10-41 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Incomplete Dominance Slide 42 10-42 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Sample Problem: Incomplete Dominance If a pink snapdragon is
crossed with a white snapdragon, what phenotypes can result? What
is the probability of each phenotype? Slide 43 10-43 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Solution Pathway: Incomplete Dominance Slide 44 10-44
Copyright The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Multiple Alleles Some traits have more
than two possible alleles for a single trait. Each person can only
have two alleles for a given trait because diploid organisms have
only 2 copies of each gene. Example: ABO blood types 3 alleles for
blood type antigens on red blood cells I A = blood type A antigens
I B = blood type B antigens i = blood type O, neither type A or
type B antigens Six possible genotypes; each individual can only
have two alleles I A I A, I A i = Type A blood I B I B, I B i =
Type B blood I B I A = Type AB blood Ii = Type O blood Slide 45
10-45 Copyright The McGraw-Hill Companies, Inc. Permission required
for reproduction or display. Sample Problem: Multiple Alleles
Allele A and allele B are codominant. Allele A and allele B are
both dominant to O. A male heterozygous with blood type A and a
female heterozygous with blood type B have a child. What are the
possible phenotypes of their offspring? Slide 46 10-46 Copyright
The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Solution Pathway: Multiple Alleles Slide
47 10-47 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Polygenic Inheritance Some
characteristics are determined by the interaction of several genes.
A number of different pairs of alleles combine their efforts to
determine a characteristic. Polygenic inheritance is common with
characteristics that show great variety within the population.
Height, eye color, intelligence, etc. Slide 48 10-48 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Skin Color Is a Polygenic Trait Skin color is governed by
at least 3 different genes. Therefore, a wide variety of skin
colors exist in the human population. Slide 49 10-49 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Pleiotropy Some genes affect a variety of phenotypes.
These genes are called pleiotropic. The disease PKU results from a
mutation in one gene. The one defective protein leads to several
phenotypes. Mental retardation, abnormal growth, pale skin
pigmentation Slide 50 10-50 Copyright The McGraw-Hill Companies,
Inc. Permission required for reproduction or display. Marfans
Syndrome Is Pleiotropic Slide 51 10-51 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
Linkage Genes that are on the same chromosome are linked. Linked
genes are inherited together more often than would be predicted by
probability. All of the genes on a given chromosome represent a
linkage group. All of the genes in a linkage group will be
inherited together. Crossing-over can separate linked genes and mix
allele combinations. The closer genes are to one another on a
chromosome, the less likely they will be separated by
crossing-over, and the more likely they will be inherited together.
Slide 52 10-52 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Autosomal Linkage Autosomes
are the chromosomes that are not involved in sex determination. Of
the 23 pairs of human chromosomes, #1-22 are autosomes. Genes on
the same autosomal chromosome are autosomally linked. #23 are sex
chromosomes. Called X and Y Slide 53 10-53 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Linked Genes Are Found on the Same Chromosome Slide 54
10-54 Copyright The McGraw-Hill Companies, Inc. Permission required
for reproduction or display. Sex Determination The sex chromosomes,
X and Y, are a homologous pair. This pair is unique because X and Y
carry different sets of genes. The Y chromosome has genes that
determine maleness. The X chromosome has a variety of genes on it,
many of which are not involved in gender determination. Slide 55
10-55 Copyright The McGraw-Hill Companies, Inc. Permission required
for reproduction or display. Sex Linkage Genes on the X or Y
chromosomes are called sex- linked. Genes on the X chromosome are
called X-linked. Males only have one X chromosome, so one copy of a
recessive allele will result in the recessive phenotype in men.
Women have two copies of X, so they can be heterozygous or carriers
of a recessive trait without showing the phenotype. Hemophilia,
color-blindness, muscular dystrophy Slide 56 10-56 Copyright The
McGraw-Hill Companies, Inc. Permission required for reproduction or
display. Sex Chromosomes Slide 57 10-57 Copyright The McGraw-Hill
Companies, Inc. Permission required for reproduction or display.
X-Linked Inheritance Patterns In humans, the allele for normal
color vision is dominant and the allele for color deficiency is
recessive. Both alleles are X-linked. People who cannot detect the
difference between certain colors such as green and red are
described as having color-deficient vision. A male who has normal
color vision mates with a female who is heterozygous for normal
color vision. What type of children can they have in terms of these
traits? What is the probability for each type? Slide 58 10-58
Copyright The McGraw-Hill Companies, Inc. Permission required for
reproduction or display. Solution Pathway: X-Linked Inheritance
Slide 59 10-59 Copyright The McGraw-Hill Companies, Inc. Permission
required for reproduction or display. Other Influences on Phenotype
Variable expressivity Some dominant traits are not expressed
equally in all individuals with the trait. Polydactylism
Environmental factors Can influence the expression of a trait
Freckles and sunlight Diabetes and diet
